Typically, insects are attracted to a light irradiated from a lighting fixture, which makes people displeased. It is known that a light which easily attracts insects is a short wavelength light with a peak wavelength in the ultraviolet. FIG. 14 shows a correlation between a wavelength of lights and an insect attractancy (see, Matsushita Electric Works technical report Vol. 53 No. 1 (MEW technical report)). In FIG. 14, “cutoff wavelength” indicates that lights having wavelengths shorter than a predetermined wavelength are cut off by a filter. Further, with reference to the case where no filter is provided, an insect attraction ratio rapidly decreases as the cutoff wavelength of lights approaches 410 nm, and the insect attraction ratio becomes almost zero at about 600 nm. In other words, by cutting off short wavelength lights including ultraviolet lights, the insect attraction ratio can be reduced.
As shown in FIG. 14, in a case where a cutoff wavelength is set to 380 nm (case 1), due to the presence of the insects that are attracted to lights in a visible region, it cannot be stated that the insect attractancy is sufficiently low. Further, in a case where the cutoff wavelength is set to 450 nm (case 2), the insect attractancy is improved. Since, however, the lights are cut off at a visible region near 450 nm, the illumination light becomes yellow, which is not suitable for use as general lighting. Furthermore, in a case where a cutoff wavelength is set to 600 nm (case 3), insects are almost not attracted to the illumination light, but the illumination light is seen as red and, thus, in reality, cannot be used as general lighting.
Meanwhile, in the illumination apparatus including an LED as a light source, by appropriately selecting LED chips or fluorescent materials, it is possible to reduce ultraviolet emissions in the output lights, and thus, when compared to fluorescent lamps and the like, the insect attractancy can be lowered. However, because there are many insects that are attracted to the visible lights emitted from the LED, it cannot be stated that the insect attractancy is sufficiently low.
In such an illumination apparatus, lights from a white LED using a first LED emitting blue lights and a yellow fluorescent material, are mixed with lights from a second LED lights with a peak wavelength of 500 nm or more, so that the insect attractancy is lowered (see, e.g., Japanese Patent Application Publication No. 2009-224148).
However, in the illumination apparatus described in the above-cited reference, in a case where the second LED lights have a peak wavelength of 500 nm or more in red light, due to the visual inability of many insects to recognize red light, it cannot be expected that the red lights repel insects. In addition, in a case where the second LED lights have a peak wavelength in yellow light, the yellow lights have a behavior inhibiting effect on nocturnal lepidopteran insects (e.g., moths). However, it is unconfirmed that this effect applies to other insects, and therefore, the effect is limited to nocturnal lepidopteran insects.